Molecular Genetics of Amino Acid Biosynthesis in Arabidopsis

对拟南芥的无性突变体eir1和eir1基因的分析表明，它是极地运输模型预测的泵。EIR1蛋白只在植物的根中表达，与一些细菌外排泵有相似之处。将进行实验，为EIR1在极地运输中的功能提供直接证据。增强和抑制外排的EIR1基因突变将在酵母中产生，这一系统为探索植物中的这一途径提供了一个独特的工具。传输实验将直接测量吲哚化合物在酵母中的外流。EIR1在吲哚乙酸(IAA)从根尖到伸长区的不对称运输中的作用将通过确定EIR1在根细胞质膜上是否存在不对称定位来检验。对eir1抑制子和增强子的基因筛查应该确定转导向重力性信号的上游和下游基因。对EIR的其他家族成员的分子分析将确定这些是不是IAA泵，负责生长素对其他组织的趋向性的影响。这些基因将被克隆，并在这些EIR1同源基因中包含显性负突变的转基因植物(在酵母试验中得到验证)将被用于构建转基因植物，然后将对其进行趋向性缺陷分析。细胞扩增的遗传途径将使用从已经开发的筛查中获得的突变来构建。其他旨在描述侧根形成途径的实验包括克隆编码ALF4的基因。AF1突变体通过内源和外源IAA抑制侧根的形成。此外，还描述了一种新的转基因植物抗盐性的工程方法。本工作的目的是确定植物激素生长素(或IAA)促进植物向向性的信号转导途径(S)。在重力论中，根部向地心弯曲。极地运输假说假设了一种外流转运体，它将IAA从根尖向上泵送到离地球中心最近的根侧。在那里，IAA抑制细胞的伸长，而对面的细胞则伸长，结果是根向下弯曲并向那个方向生长。

Analysis of the agravitropic mutant of Arabidopsis thaliana, eir1 and the EIR1 gene, suggests that it is the pump predicted by the polar transport model. The EIR1 protein, expressed only in the root of the plant has similarities to some bacterial efflux pumps. Experiments to provide direct evidence for the function of EIR1 in polar transport will be done. Mutants of the EIR1 gene that enhance and inhibit efflux will be generated in yeast, a system which provides a unique tool to probe this pathway in plants. Transport experiments will measure the efflux of indolic compounds directly in yeast. The role of EIR1 in asymmetric transport of indol acetic acid (IAA) from the root tip to the elongation zone will be tested by determining whether there is asymmetric localization of EIR1 in the plasma membrane of root cells. Genetic screens for suppressors and enhancers of eir1 should identify the upstream and downstream genes that transduce the signal for gravitropism. Molecular analysis of the other family members of EIR paralogs will determine whether these are the IAA pumps responsible for the effects of auxin on tropisms in other tissues. These genes will be cloned and transgenic plants containing dominant negative mutations in these EIR1 paralogs (validated in a yeast assay), will be used to construct transgenic plants, which will then be analyzed for tropism defects. A genetic pathway for cell expansion will be constructed using mutants obtained from a screen, which has been developed. Other experiments designed to delineate the pathway of lateral root formation involve cloning the gene encoding ALF4. af1 mutants block lateral root formation both by endogenous and exogenous IAA. In addition, a novel approach is described to engineer transgenic plants resistant to high salt.The goal of this work is to identify the signal transduction pathway(s) by which the plant hormone auxin (or IAA) promote plant tropisms. In gravitropism, the root bends towards the center of the earth. The polar transport hypothesis posits an efflux transporter that pumps IAA up from the root tip to the side of the root closest to the center of the earth. There the IAA inhibits the elongation of the cells, whereas those on the opposite side elongate, with the result that the root bends down and grows in that direction.